2 Answers

Heracross' catch rate is a low 45 (5.9% chance to capture at full HP with a normal PokeBall), so catching it will take some effort. Here's a nice technique to capture it:

Use Dusk Balls. Hunt at night, as Dusk Balls are more effective than even Ultra Balls. If you can't hunt at night, stick with Ultra Balls. Or waste a Master Ball.

Bring a Pokemon that can inflict Sleep, Paralysis or Frozen statuses. Never anything else, or else it could kill itself. Have that Pokemon use the move on Heracross.

Bring a Pokemon that knows False Swipe, to lower it's health without risking killing it. Gradually lower it's health using that or a move that won't kill it.

When it's HP is Red, and it has one of the above status conditions, throw a Dusk Ball. If it's not at night, Ultra Balls are your best bet.

In reference to trachy's comment:
On normal honey trees, Heracross is the rarest Pokemon that can appear; at only 1% chance of appearing, it is a challenge to find, let alone capture it. A technique could be:

Get some Honey and lather it on several trees. The move the better, obviously.

Wait 6+ hours for the Honey to come into effect. Don't leave it for more than a day though, or the Pokemon on the tree will disappear.

From here it's a matter of trail and error. Since Heracross is so rare, it may take many repeats of this to find Heracross. Interact with the tree to find the Pokemon. If its not Heracross, try another tree or repeat the above.

Once you find it, follow the steps from the start of the answer. Since the Pokemon that appears on the tree is determined when you actually lather it in Honey, soft-resetting can ruin the effectiveness of step 1; and on side note, changing the DS clock will not work either.

I think he might be talking more about how to find it than ways to catch it in battle.
Or maybe not, and his thing about making it easier to catch Pokemon not being explained very well on the site is just an incorrect statement he has.

Smearing honey on loads of trees will help increase chance as you can only find them on sweet scented trees. Any tree will work but they only have a very slim chance of appearing as it is.

Try using a quick ball at the start just in case that works for you. If not, Bring a a Pokemon with false swipe if you have it and use it until heracross has 1hp.

Status it with paralyze or make it sleep then ultra ball it (Pack alot of them as he can be a dirtbag to catch.) If it starts to take awhile, use Timer balls to take advantage of this and if it's night, use dusk balls.